Studies on the relationship between the cholesterol content in total high density lipoprotein and its subfractions, HDL2 and HDL3 in normo- and hyperlipidemic subjects.

Total high density lipoprotein (HDL) cholesterol and cholesterol in its main subfractions, HDL2 and HDL3, were determined in 160 normo- and 90 hyperlipidemic subjects by density gradient ultracentrifugation (range of HDL-cholesterol: 0.05-2.85 mmol/l). Both in the normolipidemics and in the combined group HDL3-cholesterol (HDL3-chol) as well as HDL2-cholesterol (HDL2-chol) showed a parabolic relationship with total HDL-chol. The results indicate, that at low total HDL-chol values almost all cholesterol is present in the HDL3 fraction, which shows a linear increase with total HDL-chol from 0 to 0.75 mmol/l. At a further increase of total HDL-chol, cholesterol is increasingly isolated in the HDL2-fraction, especially when HDL3-chol has reached its maximum (about 1.25 mmol/l). Thus, the magnitude of the absolute intra-individual variation of either HDL3-chol or HDL2-chol (in mmol/l) is related to the total HDL-chol concentration. Given the strong correlation between cholesterol in both HDL-subfractions with total HDL-chol and the inverse relationship of total HDL-chol with the risk for coronary heart disease, a rise in HDL3-chol or in HDL2-chol may be equally favorable.